Breeding of homozygotes of self-incompatible haplotype in Japanese pear (Pyrus pyrifolia Nakai)

Homozygotes of self-incompatible haplotypes are useful tools for identifying the S-genotype. So far, we have selected S-2, S-3 and S-3(sm) homozygotes. The objective of this study is to select S-4, S-5 and S-7 homozygotes in Japanese pear. '421-6' and '421-24', which were selected from among seedlings obtained from the selfing of 'Shinsui' (S4S5), are compatible with the pollen of 'Shinsui'. Pollen of '421-6' is incompatible with 'Yakumo'(S1S4) and 'Gold Nijisseiki' (S2S4), but compatible with 'Housui'(S3S5). On the other hand, the pollen of '421-24' is incompatible with 'Housui' and 'Okusankichi' (S5S7), but compatible with 'Yakumo' (S1S4). '420-50', which was selected from among the selfed seedlings of 'Okusankichi', is compatible with the pollen of 'Okusankichi'. Pollen of '420-50' is incompatible with 'Hougetsul (S1S7), but compatible with 'Housui'. The PCR-RFLP method showed only one S-RNase fragment in these three lines; that of '421-6' is digested by NdeI, that of '421-24' is digested by AlwNI and that of '420-50' is digested by AccII. These results suggest that the S-genotypes of '421-6', '421-24' and '420-50' are S4S4, S5S5 and S7S7, respectively.